Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A bone-fastening system includes an implant with a threaded screw, a
distal nut with a threaded bore, and a proximal washer which may also be
threaded. An instrument for implanting the implant includes a handle and
a barrel terminating in a holder for the washer. A c-shaped bridge
assembly has a first end connected to the barrel and a second end
including a holder for the nut in axial alignment with the washer. A
manually operated control on the instrument, coupled to an elongated
element in the barrel, causes the washer to move toward the nut, thereby
applying compressive pressure to bone portions to be fastened together. A
drive mechanism disposed within the barrel has a distal end with a holder
for the screw and a proximal end that is turned by a user, thereby
advancing the screw through the washer to the nut to fasten the bone
portions under compression. The manually operated control is preferably a
trigger that is squeezed toward the handle by a user. A separate control,
also preferably in the form of a trigger, is used to release pressure on
the elongated element in the barrel, enabling the implant to be easily
removed from the implant once in position.

Claims:

1. A bone fastening system, comprising:an implant including a threaded
screw, a distal nut with a threaded bore, and a proximal washer;an
instrument having a handle and a barrel terminating in a holder for the
washer;a c-shaped bridge assembly having a first end connected to the
barrel and a second end including a holder for the nut in axial alignment
with the washer;a manually operated control on the instrument coupled to
an elongated element in the barrel, the operation of the control causing
the washer to move toward the nut, thereby applying compressive pressure
to bone portions to be fastened together; andand drive mechanism disposed
within the barrel, the drive mechanism having a distal end with a holder
for the screw and a proximal end that is turned by a user, thereby
advancing the screw along the alignment axis through the washer to the
nut to fasten the bone portions under compression.

2. The system of claim 1, wherein the manually operated control is a
trigger that is squeezed toward the handle by a user.

3. The system of claim 1, wherein:the nut includes opposing side cut-outs
that extend into the threaded bore;the holder for the nut includes a pair
of opposing side tabs that engage with the cut-outs during placement of
the nut; andthe opposing side tabs are deformed outwardly when the screw
is advanced through the nut, thereby enabling the bridge assembly to be
remove from the implant.

4. The system of claim 1, wherein:the nut includes opposing side cut-outs
that do not extend into the threaded bore;the holder for the nut includes
a pair of opposing outriggers that engage with the cut-outs during
placement of the nut.

5. The system of claim 1, wherein holder for the washer is coupled to a
manually operated control enabling a user to orient the washer for
improved conformity with a bony surface.

6. The system of claim 1, wherein the screw includes a pointed tip that
self-taps through bone.

7. The system of claim 1, wherein the nut and washer each include a
plurality of bone-penetrating spikes.

8. The system of claim 1, wherein the nut and washer have differently
angled bone-contacting surfaces, neither of which is perpendicular to the
alignment axis.

9. The system of claim 17 further including a second control for releasing
pressure on the elongated element in the barrel for removal purposes.

[0002]This invention relates to bone arthrodesis, and more particularly to
bone fixation implants and systems and methods for installing such
implants.

BACKGROUND OF THE INVENTION

[0003]Bone arthrodesis or fusion is a process used to assist in the
healing or stabilization of impaired bones or joints. In particular,
facet arthrodesis is used to fuse the superior and inferior facet in
spinal treatment operations, Prior art systems and methods have used bone
screws which are screwed through the superior and inferior facets to
immobilize the joint so as to permit the adjoined bone sections to fuse
together. Wire has also been used to loop around the facets to immobilize
the joint. The surgical procedures that must be performed to implant the
screws or wires are difficult and time consuming. There is therefore a
need for improved bone fixation implants, devices and methods.

SUMMARY OF THE INVENTION

[0004]This invention resides in a bone-fastening system. While the
described embodiments are oriented toward direct facet fixation, one of
skill in the art will appreciate that system and method may be modified
for other applications, including translaminar facet fixation and the
setting of fractures.

[0005]The system includes an implant with a threaded screw, a distal nut
with a threaded bore, and a proximal washer which may also be threaded.
An instrument for implanting the implant includes a handle and a barrel
terminating in a holder for the washer. A c-shaped bridge assembly has a
first end connected to the barrel and a second end including a holder for
the nut in axial alignment with the washer. A manually operated control
on the instrument, coupled to an elongated element in the barrel, causes
the washer to move toward the nut, thereby applying compressive pressure
to bone portions to be fastened together. A drive mechanism disposed
within the barrel has a distal end with a holder for the screw and a
proximal end that is turned by a user, thereby advancing the screw
through the washer to the nut to fasten the bone portions under
compression. A separate control is used to release pressure on the
elongated element in the barrel, enabling the implant to be easily
removed from the implant once in position.

[0006]In the preferred embodiment, the controls are triggers that are
squeezed toward the handle by a user. The nut may include opposing side
cut-outs that extend into the threaded bore, and the holder for the nut
may include a pair of opposing side tabs that engage with the cut-outs
during placement of the nut. The opposing side tabs are deformed
outwardly when the screw is advanced through the nut, thereby enabling
the bridge assembly to be remove from the implant. The nut may further
include opposing side cut-outs that do not extend into the threaded bore,
with the holder for the nut include a pair of opposing outriggers that
engage with the cut-outs to enhance stability placement and fastening of
the nut.

[0007]The holder for the washer may be coupled to a manually operated
control enabling a user to orient the washer for improved conformity with
a bony surface. In the preferred embodiment, the screw includes a pointed
tip that self-taps through bone, and the nut and washer nut and washer
have differently angled bone-contacting surfaces with bone-penetrating
spikes, neither of the surfaces being perpendicular to the alignment
axis.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1A is a side view of a facet gun according to this invention;

[0009]FIG. 1B is a front view of the facet gun of FIG. 1A;

[0010]FIG. 1C is a side view of the facet gun with a cover removed showing
internal mechanisms;

[0011]FIG. 1D is a back view of an improved facet gun according to the
invention;

[0012]FIG. 1E is a top view of the facet gun of FIG. 1A;

[0013]FIG. 1F is a cross-section view of the facet gun of FIG. 1A;

[0014]FIG. 2A is a side view drawing of the transfacet
barrel/screw/nut/washer assembly;

[0015]FIG. 2B is a bottom view drawing of the assembly of FIG. 2A;

[0016]FIG. 2C is a top view drawing of the assembly of FIG. 2A with parts
indicated;

[0017]FIG. 2D is an oblique view drawing of the assembly of FIG. 2A;

[0018]FIG. 2E is a front view drawing of the assembly of FIG. 2A;

[0019]FIG. 2F is a back view drawing of the assembly of FIG. 2A;

[0020]FIG. 3A is an oblique drawing of a transfacet barrel assembly with a
retainer in place;

[0021]FIG. 3B is an oblique drawing of the distal end of transfacet barrel
assembly the retainer removed showing the screw, washer and nut;

[0028]FIG. 10 is an oblique drawing which shows a barrel assembly finger
release;

[0029]FIG. 11 is an oblique back view of a further improved facet gun
apparatus according to the invention;

[0030]FIG. 12 is an exploded view of the instrument of FIG. 11;

[0031]FIG. 13A is a top-down view of the gun depicted in FIGS. 11 and 12;

[0032]FIG. 13B is a side view of the gun depicted in FIGS. 11 and 12;

[0033]FIG. 13C is a bottom view of the gun depicted in FIGS. 11 and 12;

[0034]FIG. 13D is a back view of the gun depicted in FIGS. 11 and 12

[0035]FIG. 13E is a front view of the gun depicted in FIGS. 11 and 12;

[0036]FIG. 14A is an oblique, exploded view of the bridge assembly from a
rearward perspective;

[0037]FIG. 14B is an oblique representative from a front perspective of
the bridge assembly from a rearward perspective;

[0038]FIG. 14C is a side view of the bridge assembly from a rearward
perspective;

[0039]FIG. 15 provides different views of an improved nut according to the
invention;

[0040]FIG. 16A is a bottom view of the improved bridge assembly;

[0041]FIG. 16B is a side view of the improved bridge assembly;

[0042]FIG. 16C is a front view of the improved bridge assembly;

[0043]FIG. 16D is a back view of the improved bridge assembly;

[0044]FIG. 17A is one view of an improved driver according to the
invention;

[0045]FIG. 17B is a different view of the improved driver;

[0046]FIG. 17C is an exploded isometric drawing of the driver assembly;
and

[0047]FIG. 18 shows the bridge assembly from different perspectives, with
the distal nut in position.

DETAILED DESCRIPTION OF THE INVENTION

[0048]Co-pending U.S. patent application Ser. No. 10/973,524, the entire
content of which is incorporated herein by reference, describes a bone
fixation implant system and method particularly useful for percutaneous
facet fixation during minimally invasive surgical procedures. The system
includes an implant for bone arthrodesis and a bone fastening device. The
implant includes a fastener with an elongated shaft having a head at one
end and a bone-piercing point at the opposite end. A first washer has
structure for engaging the head of the shaft so as to be polyaxially
pivotable with respect to the head. A locking member has structure for
engaging the shaft. The locking member can have a second washer pivotally
engaged thereto. The bone fastening device can include an elongated
cannula with a collet for detachably engaging the first washer and for
advancing the first washer. Structure is provided for engaging the
fastener and for advancing and rotating the fastener through the collet
and through the first washer. The bone arthrodesis device further
includes a lower end portion extending from the cannula. The lower end
portion has structure for detachably engaging the locking member. The
fastener, first washer, and locking member are aligned such that the
advancing fastener will advance through the first washer, drill through
the bone, and move into the locking member. A method for performing bone
arthrodesis is also disclosed.

[0049]The following description details improvements to facet fixation
apparatus and methods, including the system and methods set forth in
application Ser. No. 10/973,524 referenced above. FIG. 1A is a side view
of an improved facet gun described in U.S. Provisional Application Ser.
No. 60/938,886, the entire content of which is also incorporated herein
by reference. FIG. 1B is a front view. FIG. 1C is a side view with a
cover removed showing internal mechanisms. FIG. 1D is a back view, FIG.
1E is a top view, and FIG. 1F is a cross-section. As with the gun
described in the '524 application, the fastener is driven with handle 102
which makes a ratcheting connection through the mechanism depicted in the
cross-section of FIG. 1F. An improvement is tab 100 which is coupled to
the washer described in further detail below. Right-left movement of the
tab 100 also moves the washer slightly clockwise and counter-clockwise,
thereby providing improved orientation of the washer relative to
recipient bone-engagement surfaces.

[0050]FIG. 2A is a side view drawing of a disposable barrel assembly 200
that mounts to the gun body of FIG. 1 by way of threaded coupler 202.
FIG. 2B is a bottom view, FIG. 2C is a top view, FIG. 2D is an oblique
view, FIG. 2E is a front view, and FIG. 2F is a back view. These figures
show the barrel assembly without the screw, nut or washers in position.
One improvement over previous designs is the provision of distal prongs
210, 212, which fit into slots in the nut described below. These prongs,
which are separated by the advancing fastener, hold the distal implant
components in position until the fastener is advanced.

[0051]FIG. 3A is an oblique drawing of the transfacet barrel assembly with
a temporary retainer 300 in place. FIG. 3B is an oblique drawing of the
distal end of the barrel assembly with the retainer removed showing the
screw 302, washer 304 and nut 306.

[0052]FIG. 4 shows different views of a bridge finger release, better
illustrating spreadable prongs 210, 212. FIG. 5 shows different views of
a bridge mount, and FIG. 6 shows different views of a flap nut. These
drawings better illustrate side slots 602, 604 which receive prongs 210,
212. FIG. 7 shows a blank version of the nut of FIG. 6 and a deformed
version wherein slot 702 is spread prior to use. With this design, the
advancing screw straightens the deformation back out with a residual
interference that locks the two components in position. FIG. 8 shows
different views of a PCS nut, and FIG. 9 shows blank and deformed
processes. FIG. 10 is an oblique drawing which shows the barrel assembly
with nut and washer in position.

[0053]FIG. 11 is an oblique back view of a further improved facet gun
apparatus according to the invention. In this case, the barrel assembly
1102 including bridge assembly 1104 is permanently affixed to the body of
the gun 1106. This is not necessary to the invention, however, as it is
contemplated to have bridge assembly preloaded with fasteners, enabling
the bridge assembly and fasteners to become coupled to a barrel assembly
and gun which is not disposable. In the case of FIG. 11, however, all
components being integrally fabricated results in a disposable item.

[0054]Continuing the reference to FIG. 11, handle 1108 is used to compress
the proximal washer against the distal nut, with the advancement of the
screw being done manually by coupling a suitable drive instrument to
socket 1110. This not only simplifies the overall design, but provides
the surgeon with tactile feedback as to the extent of screw advancement,
thereby minimizing over-tightening. Further improvements includes the
provision of a hard stop 1112 on the proximal drive end, causing
advancement to be terminated at a certain extent, thereby further
minimizing over-tightening situations.

[0055]Continuing the reference to FIG. 11, the further improvements in the
design is the provision of a release lever 1114, which disengages handle
1108, allowing the bridge to be removed from the fastened implant once
secured in position. The design continues to incorporate tab 1116, which
allows washer 1120 to rock back and forth for better cooperation with
patient physiology.

[0056]FIG. 12 is an exploded view of the instrument of FIG. 11, showing
how far fewer components are necessary, as compared to previous designs.
With the use of a manually-operated mechanism to advance screw 1202, the
need for complex ratcheting mechanisms has been eliminated. FIG. 12 also
better illustrates cupola tube 1204, which is the element used to apply
pressure to washer 1120 against nut 1122. FIG. 13A is a top-down view of
the gun depicted in FIGS. 11 and 12. FIG. 13B is a side view; FIG. 13C is
a bottom view; FIG. 13D is a back view; and FIG. 13E is a front view.
FIG. 14A is an oblique, exploded view of the bridge assembly 1104 from a
rearward perspective. FIG. 14B is an oblique representative from a front
perspective, and FIG. 14C is a side view. The design continues to
incorporate prongs 1402, 1404 which engage with indents in the nut and
spread with advancement of the screw. However, an improvement includes
outriggers 1406, 1408 which do not expand. This facilitates a
straightforward release of the bridge assembly from the nut once in
position, while maintaining stability and controlled movement of the gun
overall.

[0057]FIG. 15 provides different views of an improved nut according to the
invention. Slot 1502 engages with the outriggers just described, whereas
intents 1504, 1506 are used to receive the prongs 1402, 1404. Note that
the threads are visible through these intends, which is the reason why
the prongs are moved apart as the screw is advanced. Further improvement
is the use of differently positioned and extended fangs 1510, which
facilitate better penetration and fixation. FIG. 16A is a bottom view of
the improved bridge assembly; FIG. 16B is a side view; FIG. 16C is a
front view; and FIG. 16D is a back view. These views better show
outriggers 1406, 1408 and spreadable fingers 1402, 1404. FIG. 17A is one
view of an improved driver according to the invention, and FIG. 17B is a
different view of that improved driver. In contrast to previous designs,
which required a two-part installation process, this improved driver
allows for a one-step assembly and use process. The driver simply slides
into position, enabling the practitioner to immediately begin the
threading operation. FIG. 17C is an exploded isometric drawing of the
driver assembly. FIG. 18 shows the bridge assembly from different
perspectives, with the distal nut in position.

Patent applications by Doris Blake, Delray Beach, FL US

Patent applications by Mark Falahee, Ann Arbor, MI US

Patent applications by Phil Reed, Davie, FL US

Patent applications by Trace R. Cawley, Boca Raton, FL US

Patent applications in class Screw or pin placement or removal means

Patent applications in all subclasses Screw or pin placement or removal means